Plot points with coordinates where \(x\) and \(y\) are equal. Three points are sufficient, but more can be plotted. Draw a line through the plotted points. If \(x\) is positive, \(y\) is negative. If ...

Plotting a graph takes time. Often mathematicians just want to know the key features. These are: shape, location and some key points (such as where the graph crosses the axes or turning points).